1. Field of the Invention
The present invention relates to a pressure control valve. Further, the present invention relates an evaporation fuel discharge control device which, when fuel is supplied to a fuel tank of a car, is used to control the discharge of evaporation fuel from the fuel tank.
The present application is based on Japanese Patent Applications No. Hei. 10-106055 and 11-59674 which are incorporated herein by reference.
2. Description of the Related Art
Generally, in a car, evaporation fuel from a fuel tank is temporarily stored in a canister through an evapo-pipe, and it is introduced into an engine suitably. There is disposed a pressure control valve in the evapo-pipe.
And, conventionally, as a pressure control valve which is used in such pipe, for example, there is known a pressure control valve which is disclosed in Japanese Utility Model Publication No. Hei. 1-83976.
FIG. 17 shows the pressure control valve that is disclosed in the above-cited publication. That is, the pressure control valve comprises a cap 202 which includes a first port 201 in communication with a fuel tank, and a body 204 including a second port 203 in communication with a canister.
The body 204 includes a partition wall 205 in the interior portion thereof; and, in particular, between the upper surface of the partition wall 205 and the inner surface of the cap 202, there is interposed a first valve 206, and, inside the first valve 206, in particular, between the upper surface of the partition wall 205 and a valve body 207, there is interposed a second valve 208.
And, in the portion of the partition wall 205 that is situated on the inner side of the second valve 208, there is formed a fluid passage 209.
However, in the above-structured conventional pressure control valve, since the fluid passage 209 is formed only in the portion of the partition wall 205 that is situated on the inner side of the second valve 208, when the pressure within the fuel tank increases suddenly, it is difficult to introduce the evaporation fuel within the fuel tank through the first and second ports 201 and 203 to the canister side quickly.
Further, as an evaporation fuel discharge control device which, when fuel is supplied to a fuel tank of a car, is used to control the discharge of evaporation fuel from the fuel tank, for example, there is known a device which is disclosed in Japanese Patent Publication No. Hei. 8-189423.
Now, FIG. 18 shows the evaporation fuel discharge control device disclosed in the above-cited patent publication. In this evaporation fuel discharge control device, a tank main body 302 of a fuel tank 301 is connected to a canister 303 through an evaporation fuel passage 304.
Within the tank main body 302, there is disclosed a float valve 306 which is used to close an entrance portion 305 of the evaporation fuel passage 304 when fuel within the tank main body 302 exceeds a given liquid level.
And, in the evaporation fuel passage 304, there is disposed a switch valve assembly 307.
The switch valve assembly 307 has a diaphragm valve which divides a positive pressure chamber 307a and a back pressure chamber 307b, while the evaporation fuel passage 304 includes the positive pressure chamber 307a.
And, when the pressure on the positive pressure chamber 307a side is higher by a predetermined value or more than the pressure on the back pressure chamber 307b side, the evaporation fuel passage 304 is opened.
On the back pressure chamber 307b side of the switch valve assembly 307, there is opened a pressure introduction passage 309 which is connected to an entrance portion 308a of a fuel supply pipe 308.
And, the portion of the evaporation fuel passage 304 on the upstream side of the switch valve assembly 307 is connected to the pressure introduction passage 309 by a communicating passage 310.
In the communicating passage 310, there is disposed a check valve 311 which is structured such that it can be opened when the pressure on the upstream side of the switch valve assembly 307 is higher by a given value or more than the pressure on the pressure introduction passage 309 side.
In the evaporation fuel discharge control device of this type, if a cap (not shown) of the fuel supply pipe is removed when starting fuel supply, then the pressure on the back pressure chamber 307b side of the switch valve assembly 307 is reduced down by the predetermined value or more than the pressure on the positive pressure chamber 307a side of the switch valve assembly 307 through the pressure introduction passage 309 to thereby open the switch valve assembly 307, so that the evaporation fuel from the tank main body 302 is fed through the evaporation fuel passage 304 and is stored to the canister 303.
And, if the internal pressure of the tank main body 302 is increased due to start of the fuel supply and the upstream side pressure of the switch valve assembly 307 is thereby increased by the given value or more than the pressure on the pressure introduction passage 309 of the check valve 311, then the check valve 311, which is disposed in the communicating passage 310, is caused to open. As a result of this, a part of the evaporation fuel within the tank main body 302 is introduced through the pressure introduction passage 309 into the entrance portion 308a of the fuel supply pipe 308 and is then returned back into the tank main body 302 together with fuel which is supplied from a fuel supply gun 312.
And, if the tank main body 302 is filled with fuel, then the entrance portion 305 of the evaporation fuel passage 304 is closed by the float valve 306, with the result that the pressure on the upstream side of the switch valve assembly 307 with the communication thereof with respect to the interior portion of the tank main body 302 cut off is caused to decrease quickly to thereby close the switch valve assembly 307 and check valve 311.
And, if the cap (not shown) is mounted on the fuel supply pipe 308 after completion of the fuel supply, then the pressure of the entrance portion 308a of the fuel supply pipe 308 increases together with and equally to the pressure of the interior portion of the tank main body 302, so that the pressure on the back pressure chamber 307b side of the switch valve assembly 307 is caused to increase through the pressure introduction passage 309 and the pressure of the check valve 311 on the pressure introduction passage 309 side thereof is also caused to increase.
However, in the above-mentioned conventional evaporation fuel discharge control device, because, if the interior portion of the tank main body 302 is filled with the fuel, then not only the entrance portion 305 of the evaporation fuel passage 304 is closed by the float valve 306 but also the switch valve assembly 307 and check valve 311 are closed, the pressure on the upstream side of the switch valve assembly 307 remains as pressure equivalent to the atmospheric pressure, which causes the float valve 306 to stick to the entrance portion 305 of the evaporation fuel passage 304.
Therefore, conventionally, in order to prevent the float valve 306 from sticking to the entrance portion 305 of the evaporation fuel passage 304, for example, the float valve 306 is divided in two upper and lower stages. However, in this case, there arise other problems: that is, the float valve 306 is complicated in structure, the manufacturing cost thereof is increased, and the response property thereof is lowered.